Nitrogen Use Efficiency in Tomato ( Lycopersicon esculentum L.) and French Bean ( Phaseolus vulgaris L.) as Influenced by Coating of Urea with Neem Oil and Graded Levels of Nitrogen

In a pot-culture study, 'Arka Shrestha' tomato and 'Arka Komal' French bean were raised on red sandy-loam to compare urea coated with neem oil (2% w/w, NOCU) and prilled urea (PU) applied at 60, 80 and 100% of recommended N dose. To facilitate direct measurement of N use parameters, urea enriched with 15N (1 atom per cent excess) was used as the source of N. Compared to 'no urea' control, the application of N significantly increased dry matter production, fruit/pod yield as well as the parameters of N use. Prilled urea coated with neem oil (NOCU) was superior to PU in both the crops and produced 21% and 9% higher yield compared to the latter. Increasing the dose of N significantly increased dry matter production, yield and all parameters of N use. However, the interaction effects showed that N applied as NOCU at 80% the of recommended dose produced fruit/pod yield at par with that obtained at 100% of the recommended dose applied as PU in both crops. Corresponding fertilizer utilization achieved was 14.9% and 59.0% when 80% of N was applied as NOCU compared to 11.5% and 30.1 obtained when 100% of N was applied as PU in tomato and French bean, respectively.